Various thin layer deposition processes such as atomic layer deposition (ALD) and the many different epitaxial deposition techniques, such as chemical vapor deposition (CVD), hydride vapor phase epitaxial (HVPE) processes to name a few of the large family of deposition techniques used in manufacturing semiconductor devices are known. The processes are generally performed in device referred to as a reactor. The reactor has a production chamber in which a substrate having a surface on which a layer of a desired material is to be formed is supported by a pedestal in a region of the production chamber referred to as a “growth zone”. A gas delivery system in communication with the production chamber delivers precursor gases to the growth zone where they react and/or decompose under conditions of temperature and pressure that facilitate deposition of the desired material on the substrate surface. The reactor comprises various heating elements and pumps that are controlled to maintain regions of the production chamber and growth zone at desired temperatures and pressures.
The gas delivery system typically comprises a system of delivery flow pipes, pumps, and valves that are controlled to transport the precursor gases from their sources outside the reactor to the production chamber at desired flow rates and partial pressures. Excess quantities of precursor gases delivered to the production chamber are removed from the production chamber after delivery to the growth zone by an exhaust system. The exhaust system may comprise an exhaust flow pipe that delivers the excess precursor gases to an abatement unit, which removes toxic gas components from the excess gases before the excess gases are released to the atmosphere.
The various thin layer production processes may often be complex processes in which the quality of a deposited layer of a material is sensitively dependent on temperature, pressure and flow rates of the precursor gases used to form the layer. Generally, temperature of a precursor gas has to be maintained within an operating range of temperatures limited by lower and upper bound operating temperatures for the gas to function as required in a given deposition process. The range may be relatively small and in some instances the lower bound operating temperature may be a temperature below which the precursor gas forms an aerosol of liquid or solid particles and an upper bound operating temperature may be a temperature above which the gas undergoes pyrolysis and decomposes.
Change in gas temperature to above an advantageous upper bound operating temperature or below an advantageous lower bound operating temperature may be caused by Joule-Thomson cooling or heating as the precursor gas undergoes pressure changes in flowing through the flow pipes pumps and valves of the gas delivery system from a source to the growth zone.